This invention relates to an outboard motor and more particularly to an improved construction and component layout for a four cycle outboard motor.
In outboard motors, it is a common practice to employ a two cycle internal combustion engine as a power unit. Such engines have considerable advantages for this particular type of application. Because of their relatively compact nature, simple construction and high relative output for their displacement, they are well suited for this purpose. However, because of emission concerns, two cycle engines are being replaced by four cycle engines in these applications.
There are, however, not only space problems in connection with substituting four cycle engines for two cycle engines, but there is also a problem in that the engine has more complexity and the layout of the engine and its components presents considerable problems for the designer. To further complicate the problem, frequently the engine is provided also with an alternator so as to charge a storage battery or electrical system in the associated watercraft. The alternator must be driven off of the engine and this further complicates the positioning of components in the power head and the driving of those components which must be driven from the engine. Furthermore, there is a strong desire to maintain the outboard motor power head in such a nature that it can be easily serviced, particularly while still attached to the transom of the associated watercraft.
It is, therefore, a principle object of this invention to provide an improved outboard motor construction particularly employing a four cycle internal combustion engine.
It is a further object of this invention to provide an improved four cycle engine powered outboard motor having accessories driven by the engine and positioned in a compact and yet serviceable manner.
A further difficulty with the use of four cycle engines is caused by the fact that the crankshaft of the engine is normally at the front of the power head to facilitate connection to the drive shaft. The drive shaft is normally placed forwardly in the drive shaft housing. Because of the fact that the engine generally uses overhead valves and at least one overhead camshaft the center of gravity of the outboard motor and/or the power head is displaced rearwardly. This can cause vibration problems.
It is, therefore, a further object of this invention to provide an improved outboard motor construction particularly employing a four cycle internal combustion engine with a forwardly located center of gravity.